The invention relates to a device for expanding bags and slipping them on to a filling neck, especially bags with side folds, which are fed individually on to an aligning table, with the bag opening being positioned at the front, i. e., at the end of the aligning table toward the filling neck, and to the bag-handling method carried out by that device. A device of the aforementioned type is known from German Offenlegungschrift No. DE 38 40 646 Al. With this device, the bags are first pulled backwards from a bag store, with the closed bottom end of the bag being positioned at the front in the conveying direction. Subsequently, with the conveying direction being reversed, the bags are pulled on to the aligning table, with the bag opening being positioned at the front. The equipment components required for this process may be used, without having to be modified, for the device in accordance with the present invention. The aligning table forms part of the device in accordance with the present invention; the means for expanding and slipping on the bags is mounted on the same frame as the aligning table.
There are prior art equipment components for expanding and slipping on bags, for example, the automatic suspension device OMPB II for open bags of Chronos Richardson GmbH, in which the bag opening may be vacuum-loaded and expanded by first suction elements which are movable towards the lower bag wall and second suction elements which are movable towards the upper bag wall and which are each arranged in the region of the front bag edge, so that the bag opening is expanded by the separation of the bag walls in the areas adjacent the open end of the bag. Furthermore, there are provided means designed as expanding arms which move into the bag opening and separate therein so that the bag opening is expanded fully. The bag is gripped and held merely by being mechanically expanded A pivot movement of the expanding arms around a horizontal axis positioned above the aligning table ensures that the bag is now slid on to a filling neck where it is held by bag clamps.
The slipping-on device of the above-described type has a disadvantage in that, in the region of the bag edges, the bag cross-section is opened fully, which means that after filling the bag it is no longer possible to produce a clearly defined side fold in the region of the bag opening. This is particularly disadvantageous when closing bags with side folds, but it also has a disadvantageous effect when closing simple flat bags without multiple side folds. When using prior art closing devices, edges of the open end of the filled bag initially had to be folded back before sealing the bag by sewing the folded edges together, which is a complicated and expensive process.
The manufacturer named Slidell (USA) produces devices for expanding and slipping on bags, in which the bags are expanded exclusively by suction means acting on the bag faces, while there are provided gripping means which, at the same time, hold the side folds of the bags, especially in the case of laterally folded bags, in their original position until the bag has been slipped on to the filling neck. The suction means exert their effect near the edge of the bag. Consequently, they restrict the freedom of movement of the bag clamps at the filling neck to be pressed against the slipped-on bag, and so before the clamping-on operation, they have to be moved back in a pivot movement from the rear of the bag too as viewed from the aligning table. Such a device is suitable for very stiff bags only, because during the high-speed slipping-on operation it is possible for the bag opening to collapse and cause a system malfunction.